1. Field of the Invention
The present invention relates to an image processing device and an image processing method for embedding digital watermark information in input image data so that the digital watermark information is not perceptible to human eyes, and to a storage medium for storing the image processing method.
2. Description of the Related Art
Recently, various types of information including text data, image data, and audio data have been digitized due to rapid development and dissemination of computers and computer networks. Digital information is advantageous in that it does not deteriorate by aging and that it can indefinitely and reliably store information. In contrast, the digital information can be easily duplicated, causing a serious problem in copyright protection.
Therefore, security techniques have rapidly become important for copyright protection.
One type of copyright protection technique uses an “digital watermark”. The digital watermark technique embeds the name of a copyright holder or the ID of a purchaser in digital image data, audio data, or text data so that the digital watermark is not perceptible to a person. Hence, it is possible to track unpermitted usage by illegal copying.
Besides the copyright protection, the digital watermark is applied to a technique for detecting interpolation in digital data by embedding the digital watermark in advance and by matching information using a digital data embedding rule.
Since the digital watermark technique embeds information by processing a portion such that the change in digital data is not perceptible to a person, there is a trade-off among the quality compared with the original, the resistance of the digital watermark to being lost when image data is attacked or distorted, and the amount of embeddable information of the digital data in which the digital watermark is embedded.
Hitherto, the digital watermark has been embedded in a gray-scale image by simply regarding the gray-scale image as gray-scale image data and converting the gray level. This results in serious image deterioration.